A stator coil of an electric motor or the like is wound around a cylindrical stator core. A plurality of teeth is provided at equal angular intervals on an inner periphery of the stator core. Slots are formed respectively between adjacent teeth. A wire forming the coil is wound around the teeth through a pair of slots formed on either side of one or a plurality of teeth.
A coil end of the wire wound around the teeth projects in an axial direction from an end face of the stator core between the pair of slots. When the wire is wound across a plurality of teeth rather than a single tooth, or in other words when an extra slot exists between the pair of slots through which the wire is passed, the coil crosses a coil passed through the extra slot in a motor axis direction. The coils cross at the coil ends. The number of crossed portions differs according to the pitch of the coil windings, or in other words the number of teeth across which the coils are wound, such that the number of crossed portions increases in accordance with the pitch of the windings.
When the coil ends are crossed, a length by which the coil ends project in the axial direction from an end face of the stator core increases, and to suppress the length by which the coil ends project in the axial direction, lead wires of the crossed coil ends are conventionally woven into a mesh form, for example.
With this method, the wires forming the coils are woven one at a time, leading to an inevitable increase in the complexity of a coil winding operation. To facilitate the winding operation, JP2010-166803A, published by the Japan Patent Office in 2010, proposes winding the coils by fitting a wire assembly, which is formed by gathering together a plurality of wires in a coil shape, into a pair of slots, and forming an axial direction step in advance on a coil end of the wire assembly by providing a crank portion on the coil end.
In this conventional technique, coil ends can be crossed easily by passing a lead wire assembly of an adjacent coil through a space formed between the coil and the end face of the stator core by the step provided on the coil end.